ABSTRACT
Thermal Cycler is the main part of the Polymerase Chain Reaction (PCR), which becoming a gold standard for Covid-19 diagnosis. The virus multiplication in an order to a detectable concentration is done by placing the virus solution at a deterministic temperature cycle. The solution is placed in a small tube inserted in a temperature block. Temperature distribution of the thermal block is important to make all the tube with sample treated at the same at desired target temperature. Study on the thermal block made of aluminium 7075 was simulated using fluid dynamic finite element method. Heating and colling to the target temperature was done by providing heat source and heat absorber. The temperature distribution on the surface was mapped. The temperature gradient perpendicular to the heat source was calculated. Assuming the environment of the thermal block was still air, the heating and cooling speed at given heat source and heat removal were calculated using the model. The temperature gradient from the top surface to the bottom surface is less than 2.5?. The temperature difference among point at the surface is less than 0.1?. © Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence.
ABSTRACT
Polymerase Chain Reaction (PCR) becomes one of the essential tools during the COVID pandemic. The heart of the PCR is a thermal cycler. The thermal cycler is a temperature cycle instrument that changes and maintains the vial sample's temperature at a specific target temperature. A simple thermal cycler can be made using thermoelectric as the heater and cooler to control the temperature state. The thermal block temperature distribution is important to make all the vials treated at the same temperature condition. The thermal distribution of an aluminum block as the thermal block for a portable PCR was calculated using the finite element method. The heat source and cooler with a power of 60W were placed at the bottom of the aluminum block. The temperature gradient inside the aluminum body, where the vial was placed, was calculated. The heating and cooling speed were calculated using the model. It was found that the temperature difference between the bottom surface and top surface of the aluminum block is 2.5°C during the transient time. The temperature distribution in a horizontal direction is homogenous, with a temperature difference among the surface being less than 0.01°C. The time required to heating from 24°C to 95°C is 31.05 seconds while cooling from 95°C to 55°C can be reached in 18.05 seconds. © 2021 Institute of Physics Publishing. All rights reserved.
ABSTRACT
Ultraviolet Light Emitting Diode (UV LED) is becoming popular, especially during the Covid-19 pandemic. UV LED has a specific wavelength with relatively narrow bandwidth, especially the one that has a shorter wavelength. On the other hand, UV LED has advantages in its low power consumption, compact size, and longer lifetime. This work shows that a wider bandwidth can be elicited by combining multiple UV LED sources. We have measured several low-cost UV LED, which is used as a germicidal lamp using a portable spectrometer that can detect a wavelength from 200 nm to 850 nm. The combined UV LED spectrum light ranges from 254 nm UVC to 400 nm UVA. The light spectrum produced by the LED shows a form of the Gaussian distribution model. Some LEDs have a peak wavelength at UVC around 270nm, and LEDs have a peak wavelength around 400nm at UVA. We can conclude that the low-cost UV LED can be used as a light source for portable or field spectrometers for specific wavelength.